1. Field of the Invention
This invention relates to materials and methods for producing a negative tone resist pattern on a substrate when irradiated by actinic radiation and developed in a plasma atmosphere.
2. Description of the Prior Art
A process of dry etching to form negative resist patterns is described in U.S. Pat. No. 4,232,110, assigned to the same assignee as the present invention. In that technique, a film comprising a host polymer and one or more monomers is selectively irradiated to reduce the mobility of the monomer or monomers in the irradiated region, referred to as "locking". The film is then fixed, typically by means of heating, with or without a vacuum, to substantially remove the unlocked monomer mainly from the unirradiated region. It is then etched by means of a plasma, typically comprising oxygen. The locked monomer reduces the rate of etching in the irradiated region so that when the unirradiated region is etched down to the substrate, a negative resist pattern is formed. It is also disclosed therein that monomers containing silicon tend to yield negative resist patterns having a greater final thickness for a given initial thickness, as compared to typical nonsilicon-containing monomers.
It is also noted therein that bromine-containing host polymers are typically suitable for use with rhodium and certain other types of X-ray radiation sources. However, no silicon-containing monomer is therein disclosed that can be sufficiently locked into the brominated host polymer disclosed therein to yield a useful resist pattern. It is desirable to find other resist materials, including ones that yield improved sensitivity of the resist film. It is additionally desirable to find monomers that can be locked to a significant degree in a host polymer containing bromine.